The AFFIRM Study is a two-arm clinical trial of high risk patients with documented atrial fibrillation and a high risk of recurrence, morbid events, and death. The treatment will be randomized to rhythm control and anticoagulation, or rate control and anticoagulation. Consenting adults with a qualifiying episode of atrial fibrillation within 30 days and considered to be at significant risk for stroke will be categorized as single episode (in which case sinus rhythm will be restored prior to randomization) or recurrent episodes (2 or more episodes in the past 6 months). The primary endpoint of the trial is total morbidity. Secondary endpoints include stroke, intracranial hemorrhage, disabling anoxic encephalopathy, major non-CNS hemorrhage, cardiac arrest, cost of therapy, quality of life, and functional status.